Purification of phosphorus by a zero pollution zone melting technique

Abstract

This article introduces an efficient, low cost, and clean (zero pollution) zone melting phosphorus purification technique. We have successfully removed arsenic from solid phosphorus by melting a narrow region and making the resulting liquid zone travel slowly through a relatively long ingot of phosphorus. This technique can reduce arsenic concentration in solid phosphorus from 100ppm to 10ppm in a specific condition. Purified solid phosphorus can be used to produce 85% phosphoric acid with arsenic concentration of 2.8ppm as an additive in the food industry (lower than both the Food and Drug Administration standard (FDA) and the Food Chemicals Codex standard (FCC) of 3ppm for food grade phosphoric). We applied the phase-field model to establish a system of PDEs and numerically obtained a continuous melting zone moving along with the heater.